Do you mean the parallax modules or the raw mlx90614 device? If its the parallax modules then the link in the above post is the place to go, its basically a serial interface. Otherwise as Leon said, the raw module has a SMBus interface, I have interfaced with it using a I2C implementation, the main difference is SMBus has a min clock speed as well as a max clk speed. The pic i2c interface should handle that without problem.

Thanks for the quick reply, I bought the parallax modules. So I guess Serial is the way to go. I2C uses 2 pins, a clock and a signal pin. However the module only has 1 pin, is it safe to omit the clock pin in this case?

I can not communicate to it. I have read the datasheet and have seen the examples.
I am using a microchip pic (16F628A). According to the datasheet, first i do a reset to the module (a 0 in reset pin for 5 ms and then a 1 forever)
Then i send in hexa this sequence

What are the serial parameters that you are using? Baud rate, data bits, stop bits, etc?

Is the library that you're using meant to be used with something like a MAX232 and then to a serial device? If so then the serial data may be inverted. There may be an option to invert the signal for a logic level connection.

How is everything wired up? Can you verify that you have the proper pins defined and connected. With the PIC do you have to setup the pins as inputs and outputs or does the library handle that?

I am using an UART SOFTWARE library and i guess i can not look inside these libraries... I looked everywhere and i do not know how to access to the code...

I use 2400 as the baud rate, and non inverted logic (this is taken as a parameter to the function init).

I have checked up the connections.

I connect PORTA.F6 as tx and PORTA.F7 as rx. This to SIG through sn74ls126AN (tristate buffers) and sn74ls04N (inversor) to assure that tx and rx are not used together (the enable with a pull up resistor).

I connect PORTB.F4 to reset and GND (0V) and VDD (5V).

I set the proper pins as outputs or inputs (all of them), i have checked it now.

Maybe it is something in the protocol that i don't know...
I can see the message sent by the PIC but there is no response...